Process of engraving



Patented Mar. 22, 1932 JULES ROBERT GU''BABD, Ol' BAGNOLET, FRANCE PROCESS Ol' ENGRAVING No Drawing. Application med August 3, 1828, Serial No. 297,381, and in France August 3. 1927.

My invention relates to a process of en graving which is suitable indiscriminately for the production of all sorts of plates, such as lithographie plates, plates in intaglio of 6 copper-plate engravlng character, typographical plates in relief, transparent plates and so on.

Itis old to cover a surface on which engraving is to be done with a varnish or equivalent coating (mixture of wax and resin,

softened gutta-percha, etc.).

The present inventionrelates to a specific varnish intended for this purpose and by means of which it is possible to obtain all kinds of plates: lithographie, intaglio, relief, transparent, etc. Where the term transparent plate is employed, it is intended that the varnish according to the application should be applied on either a transparent 4'or translucent support, such as glass, gelatin,

or cellulose fibre. The negative obtained on such support presents an opaque appearance' on a A transparent base. Thls varnish is formed of cellulosic ethers or esters and gum resins dissolved in a volatile solvent, the` evaporation of which first causes the formation of a jelly from a part of the solid constituents of the varnish, the other solid constituents remaining dissolved within said jelly, solidifying at the end -of evaporation in subdivided form. The varnish according to the invention is obtained, for example, by a'mixture of a solution of gum resins in alcohol-ether and a solution of the ether or ester of cellulose in acetone. Such a varnish forms on the support receiving it a dry white opaque dull layer or stratum forming a surface resembling that of Bristol board, and

at all concerned'with such coeiiicient. lIt is intended to state simply that the stratum of white enamel does not readily deteriorate when rubbed.

The drawings represent by way of exam' ple the application of themethod by the obtention of a negative in intaglio.

Fig. 1 is asection of the bare support;

Fig. 2 shows the. same support covered by a sub-strata;

Fig. 3 represents the support with the addition of a strata of white enamel above the sub-strata;

Fig. 4fshowsthe ysupport of the plate after v tracing the design;

Fig. 5 is substantially identical with Fig.

4, but .illustrates the plate after vitriicationv of the white enamel strata being heated and after scratching of the sub-strata in intaglio; Fig. 6 represents thenegative after` etchingj while ig. 7 shows the preparation for an impression after elimination of the remainder of the white enamel strata and of the substrata.

In addition, and this is extremely surpris.

ing in view ofl its character, this stratum is porous and permeable, that is to say, that it can absorb even an aqueous liquid, which does not inflate or dissolve. It can thus absorb sensitizing baths, and photographic im ages may be made directly on it.

But if this stratum is heated to a moderate temperature, it softens, ceases to be porous, and after cooling becomes hard and impermeable to aqueous liquids, the lines and the point tracings (etching) being altered. The support may then, .by the character given it, be attacked by the usual mordants to produce an intaglio plate.

` If the operation is carried out on a gelatinized support the following procedure 1s employed: the design is traced in intaglio by scratching the white enamel stratum. Where the gelatin is thus exposed, it is painted with a solution of alkaline bichromate. On subsequent exposure to the light the bichromated gelatin is insolubilized around the scratched lines. Subsequently, the white enamel is removed by means of any of its solvents. There is thus obtained in a simple manner a dra w- 1n in ink which can be carried over to anfinal etching of the support, may produce an' embossed plate.

On the supporting coating of white enamel the design is traced by scratching the said enamel 1n intaglio. The support is then heated to vitrify the white enamel. If the iss support has received avpreliminary undercoating before application of the white enamel, the under-coating is then dissolved around the scratched lines. In such cases the ne ative undergoing preparation is recovere by a coating of bitumen of Judea, dissolved-for example in benzine. After dessication, the white enamel is treated by a solvent thereof such for example as methyl alcohol. The solvent is of such nature that it cannot dissolve the bitumen. It merely swells the same, and penetrating by endosmosis through the swollen stratum of bitumen, dissolves the white enamel everywhere the latter still remains. It is then sufficient to lightly rub the stratum of bitumen, for example, through the aid of a plug of cotton, in order to remove Athe said bitumen except at the scratched lines. An etching of the support at that time permits the obtention of` a nega-tive in relief, the support being protected at the scratched lines by means of the bitumen.

Instead of spreading the varnish directly on the support, it is preferable to first apply or produce on said support an adherent under coat of a. lmaterial whose colorl differs distinctly from that of the Varnish and which is not affected by the tool, in such wise that it protects the metal against biting from the tool. The said under coat which 1s likewise not affected by the solvents of the varnish, brings out the lines traced on the coat of varnish, without the artist being eventually dist-urbed by reflection from the su port when stripped in the vicinity of the lEines. Furthermore the said under coat isolates the coatof varnish from the support and favors the removal of said coat of varnish in the vicinity of the lines. It furthermore checks the direct action of the reagents to which the plate is subjected during the process on the support. When the said under coat is finally destroyed, all of the small impurities are removed with it which would be disposed directly on the support be diliicult to make disappear completely and which has always prevented obtaining perfectly satsfactory results.

` One may obtain very simply, Von most supports, an under coat which is black and very suitable' by applying thereto one or Several successive coats of a composition having a gallate of iron base such as that given by way of example further on.

I will now indicate by way of example the compositions in their various proportions utllized for carrying my process into practice.

VARmsH Fon WHITE ENAMEL After dissolution solutions A and B are mixed, decanted and then 15 to`20% (according to the quality of the gums employed; of Y a solution of dry nitrated cotton or cellu oid with 10% acetone are added.

UNDER COAT On the support which is scraped when necessary is spread with a brush the composition below given which is equalized with a large fiat brush.

Alcohol 100 cubic cm. Gallic acid 20 grams.

After dissolution is added:

Water 200 cubic cm. Perchloride of iron at 45 Baume 10 cubic cm.

The first coat is allowed to dry during which time the color becomes accentuated. One or more additional coats are applied which are allowed to dry also and the whole rubbed with a woolen rag which gives brilliancy to the coat.

For removing the gallate of iron under coat numerous expedients may be employed. I may utilize among other things a 1 to 2% solution of oxalic acid. Furthermore in the embodiment including bitumen, the gallate of iron under coat may very frequently be preserved in the vicinity of the lines.

While I have described what I deem to be the preferable form of my process I do not wish to be limited thereto as various changes might be made in the proportions of the constituent elements employed without departing from the invention as comprehended within the scope of the appended claims.

Having described my invention what I claim as new and desire to secure by Letters Patent is:

4l. A method for preparing a surface for the printing which comprises covering al support with a varnish composed of cellulosic derivate and resinous gums in solution with a volatile solvent, evaporating said volatile solventl in order to form a ljelly of one of said solid'constituents and to se arate the l remaining solid constituents in fine y divided form in said jelly, drying said coat of varnish to render it opaque, friable and porous, and tracing a design by removing the said coating of varnish Ialong the lines of the said design for the purpose disclosed.

2. A method for preparing a surface for the printing, which comprises covering a support with a varnish composed of a solution of resinous gum in ethyl alcohol and ether (C21-PPO mlxed with a solution of cellulosic ester in acetone (CH3)2CO, evaporating the solvent for drying said coat of varnish to render it opaque, friable and porous, tracing a design by removing the said coating of varnish alongthe lines of the said design for the purpose disclosed.

3. A method for preparing a surface for the printing, which comprises covering a support With a coat of a substance having adhering properties, of a different shade that the varnish to be subsequently applied thereto and unaffected by the solvent of said varnish or an engraving tool, covering said adherent coating with a varnish composed of cellulosic derivate and resinous gum ina volatile solvent, drying said coat of varnish to rendez` it opaque, friable, and porous, tracing a design by removing the said coating of varnish along the lines of the said design and dissolving the adhering substance alon the lines of the design, for the purpose disc osed.

In testimony whereof I hereunto affix my signature.

JULES ROBERT GUERARD. 

